The purpose of this study was to clarify the effect of lansoprazole on basic fibroblast growth factor (bFGF) during the healing of gastric ulcers in comparison with famotidine and rebamipide. Alteration of the localization and concentration of bFGF was examined in gastric mucosa obtained endoscopically from ulcer patients. The bFGF content was estimated by enzyme-linked immunosorbent assay and the localization of bFGF immunoreactivity was determined by indirect immunohistochemical study using monoclonal antibodies. In the lansoprazole-treated cases, the content and the histochemical immunoreactive area of bFGF significantly increased 4 weeks after the treatment, compared with the group treated with rebamipide and the control group. In the famotidine-treated group, the concentration of bFGF significantly increased, compared with the rebamipide-treated group, and not with control. The number of binding sites for [125I]bFGF, as determined by in vitro autoradiography, also significantly increased in the lansoprazole-treated group. Therefore, an increase in bFGF concentration and receptor distribution was shown to be brought about by treatment with lansoprazole.